The present invention relates to an improvement of a vibratory bowl feeder which is used in orienting and feeding the machine parts automatically, and more particularly is concerned with a new-type motor-driven vibratory bowl feeder wherein the bowl performs linearly or non-linearly the tilting or elliptical vibration.
For the purpose of automatically orienting the machine parts and the other articles such as, for example, powdery or granular substance, and feeding certain of automatic manufacturing apparatuses such as automatic assembly machines, automatic processing machines, automatic packing machines or the like with these materials by the necessary amount at a time, vibratory bowl feeders, which were driven by an electromagnet (solenoid), were widely used heretofore. These kinds of vibratory bowl feeders are constructed in such manner that a cylindrical or saucer-like vessel, namely a bowl, wherein the machine parts and the other articles are to be stored, may be supported by several sets of plate springs which tilt at a certain angle, that an iron piece, which is stuck to the underside of the bowl, will be made to be vibrated in the vertical direction and simultaneously be put into the angular or horizontal vibration around the vertical shaft, and that the thus resultant vibration in the oblique direction can be transmitted to the bowl. As a result, the machine parts and the other articles standing on call within the bowl are conveyed upwardly along a spiral track provided on the internal circumference while being oriented by some attachments fitted up parallel to the periphery of the above track, thus being carried out of the delivery port at the terminus of the track.
There is utilized here the vibration peculiar to the bowl containing the machine parts with the addition of the other sections being supported by several springs as of iron pieces as a whole. In this case, the number of vibration of the solenoid as a driving source will take a fixed value dependently on the frequency of the power source, so that it is inevitable to decide the strength of the supporting springs in order that both the frequencies may be brought into accordance with each other in consideration of preventing the unbalance between the form and weight of the bowl and the weight of the attachments or the machine parts. What is more, the adjustment of the gap (air-gap) between the armature and the solenoid, and of the setting angle of the supporting springs governing the delivery velocity, and so on requires the one-piece job-like adroitness of very high grade. Accordingly, the adoptation of such a construction could not help being too much expensive conjointly with the use of the solenoid and related parts.
In the apparatus of such a construction, on the other hand, the delivery velocity of the machine parts comes to be dependent on the amplitude because of the definite and unchanging vibration of it. In case of the amplitude being too large, the articles which drift away from the delivery path can not keep in touch with the latter after once having run against it, as a result of which the movement becomes unstable, the efficiency drops, and the delivery velocity is restricted under a certain limit. In addition, as the amount of the articles put in the bowl changes, the number of vibration of its own nature fluctuates, giving rise to the unreasonableness attributable to the gap between itself and the frequency of the solenoid. Such was the fault of the apparatus of this kind which would also call forth the lowering in performance.
With the object of avoiding such an inconvenience, there is being proposed a variety of improvements what by coating the internal face of the bowl with urethane resin and the like in order to heighten the coefficient of friction, and what by employing high-power plate springs and solenoid in order to bring about the stability of vibration. However, so long as the bowl is supported with the use of plate springs and is driven through the aid of solenoids, it is impossible to completely eliminate the above-mentioned drawbacks.
As for the aforesaid angular vibration, this results from the vertical vibration. There is no phase difference between them. Accordingly, the oblique vibration composed of these two produces a straight-line simple harmonic motion in the direction perpendicular to the plate springs. For this reason, the backward slip is liable to happen between the conveyed articles and the surface of the track by any means, so that, even though increasing the number of vibration or the amplitude, it has been hard to obtain so much effect as yet. In order to eliminate these defects, there have been developed such methods or devices as to be able to create the vibration describing an elliptical locus by employing two sets of the supporting plate springs and the solenoids, one set used for the angular vibration and the other used for the vertical vibration, and thereby by making both solenoids each generate the vibration having the phase difference, respectively (for example, Japanese Official Pat. No. 7289-1969, and No. 32368-1969). However, these kinds of things have scarecely been used in general so far because of their complicated structure, difficulty in adjustment, and expensiveness.
The aforesaid angular vibration is the sine wave vibration, namely, the linear vibration, whose motion is one and the same both in the conveying direction and in the reverse direction. Accordingly, here tends to happen the backward rise or jump between the articles and the surface of the track at any rate, so that it was impossible so far to prevent the lowering of the efficiency of conveyance or to avoid the occurrence of noise. In other words, at the backward lower end of the oblique vibration, the acceleration in the forward direction amounts to the maximum. If this is greater than the frictional force between the articles and the surface of the track, the articles are subject to the backward rise. On the other hand, at the forward upper end of the oblique vibration, the acceleration in the vertical direction reaches the maximum. If this is greater than the acceleration of gravity (g), the articles drift away from the surface of the track to jump. In order to get rid of such a state of things, ideally speaking, it will be commendable to cause the non-linear vibration to be created by discriminating between the time of forward motion (conveyance of the articles) and the time of backward motion to make them have the difference in the number of vibration, respectively. However, it may be difficult, or rather impossible, to expect such a good thing from conventional devices which are only so designed as to be supported by solenoid-driven plate springs. Hence, in conventional vibratory bowl feeders, various kind of contrivance were thought of for the purpose now of coating the inside of the bowl with rubber, urethane resin and the others to increase the frictional force between the articles and the surface of the track, on one side, and to minimize the noise produced by the collision of the articles with the surface of the track, on the other hand, and now of holding back the occurrence of noise by reducing the amplitude. Nevertheless, it was impossible to silence the noise caused by the article-against-article collision. It would be a mere waste of words, but there was not a choice for feeders of such construction as described above but to be enveloped as a whole in a soundproof equipment. Such being the case, general-purpose vibratory bowl feeders heretofore in use were subject to various sorts of limitations and controversial points about their function and construction on account of employing solenoids in the capacity of the driving source.